1. Field of the Invention
The present invention relates to a method of regulating the luminous flux or current of ionized or turned-on vapor discharge lamps, especially metallic vapor lamps, such as mercury vapor lamps.
2. Description of the Prior Art
Mercury vapor lamps serve not only as sources of light for illuminating industrial plants, streets, and/or athletic stadiums or arenas (via floodlights), but are also used for technological processes as ultraviolet emitters. Thus, for example, in the printing industry, ultraviolet-reactive inks and lacquers are being utilized more and more frequently. These inks and lacquers dry very rapidly when exposed to ultraviolet light, and in addition permit handling of the surface quality (for example, by imprinting low quality paper or cardboard with ultraviolet lacquers, the impression of high quality special material can be produced). When the necessary ultraviolet irradiation equipment is set up, the assumption is made that the imprint material will pass continuously through the ultraviolet drying stage. However, as a rule, the imprint material in fact does not pass continuously through, so that where the drier takes a large amount of power, about 10 kW up to more than 100 kW of energy could be saved if the radiation sources were shut off or at least cut way back during interruptions in the passage of imprint material. In addition, reducing the power during these interruptions increases the life expectancy of the ultraviolet radiation sources.
Like all other vapor discharge lamps, mercury vapor lamps have the drawback that after they have been shut off, they must cool off to such an extent that all of the metallic vapor has been condensed. In addition, when the lamps are turned back on, an ionizing process takes place during which the condensed metal vaporizes; this takes several minutes. Due to the considerable lag time, this manner of regulating the power is not suitable. When radiation sources of this type are operated far below the nominal or rated load region, there exists the danger that as a result of the radiation source being cooled off to too great a degree, the arc discharge that generates the radiation will collapse, which has the same consequence as if the radiation source were actually shut off.
An object of the present invention therefore is to provide a method of regulating the operation of vapor discharge lamps, and hence for regulating the luminous flux or lamp current emitted by these lamps, with the inventive method at all times assuring that the radiation source can be operated below the rated load region, and can also be switched, without time delay, from a partial load range to a full load range.